>I have noticed that the National Semi 50Khz "Simple Switchers"
>seem to generate less EMI than the higher frequency ones.
>Just a place to start.

Well, that is a rule of thumb for switchers, lower the frequency, lower the
EMC, but the cost is larger inductors.

Another device you may like to look at is Linear Technology LT1777 which is
a 100kHz device, but allows you to program the dI/dt to minimise noise, and
has internally limited dV/dt.

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist